1. Field of the Invention
The present invention relates to a photovoltaic device for use in a solar battery, a photosensor, or the like, the photovoltaic device being constituted by stacking a semiconductor layer made of non-single-crystal semiconductor material, which contains silicon atoms, and a transparent electrode made of an indium oxide, a tin oxide, an indium-tin oxide or the like. More particularly, the present invention relates to a photovoltaic device made of amorphous silicon type semiconductor material (fine crystal silicon type semiconductor material included) or polycrystal silicon type semiconductor material as the non-single-crystal semiconductor material.
2. Related Background Art
A transparent electrode is an important component which relates to the performance of a photovoltaic device. Hitherto, the transparent electrode has been made of an indium oxide, a tin oxide, or an indium-tin oxide formed into a film by depositing the employed material by spraying, vacuum evaporating, ion plating, sputtering or the like.
The light transmissivity and the specific resistance of the transparent electrode, thus formed, are parameters which directly relate to the performance of the photovoltaic device. Also conditions under which the transparent electrode is deposited, for example, the temperature of the substrate, the degree of vacuum, the deposition speed, and the like are important parameters which affect the quality of the semiconductor layer which is positioned adjacent to the transparent electrode.
Results of a study of the relationship between the photovoltaic device and the transparent electrode have been recently disclosed in "Optical Absorption of Transparent Conducting Oxides and Power Dissipation in a-Si:H pin Solar Cells Measured by Photothermal Deflection Spectroscopy," by F LeBlanc and J. Perrin et al., Technical Digest of the International PVSEC-5, Kyoto, Japan, 1990, pg. 253, and "Improvement of Interface Properties of TCO/p-layer in pin-type Amorphous Silicon Solar Cells," by Y. Ashida, N. Ishida, and N. Ishiguro et al., Technical Digest of the International PVSEC-5, Kyoto, Japan, 1990, pg. 367.
Furthermore, a method of reducing the resistance of the transparent electrode by stacking an indium oxide film and a tin oxide film has been disclosed in Japanese Laid-Open Patent Application No. 54-134396.
However, there is a desire to further reduce the resistance of the conventional transparent electrode composed of indium oxide, tin oxide, or indium-tin oxide.
Furthermore, the transmissivity, the photovoltaic force, and the photoelectric current must be further improved.
Since photovoltaic devices have been widely used recently in a variety of conditions, a separation has taken place between the transparent electrode and the layer which is positioned in contact with the transparent layer, depending upon the conditions of use.
In addition, the problem of short circuits may arise when the photovoltaic device is repeatedly subjected to a heat cycle for an excessively long time.